Method of producing an end thickening in tubular bodies made by rolling with skew rolls



Aprll 30, 1935. H. ESSER 1,999,324 METHOD OF PRODUCING AN'END THICKENING IN BULAR BODIES MADE BY ROLLING WITH SKEW R0 Filed April 24 Patented Apr. 30, 1935 "UNITED STATES PATENT OFFICE 3 Claims. 80-62) The forming of a thickening of the wall at the end oftubes is of great importance for the connection of the tubes with one another and cannot be eiiected conveniently by the tube manufacturing methods usually employed. Hitherto a thickening at the end has usually been produced subsequently on the smooth tube through the end of the cut-off tube being. heated and upset in a die with a mandrel of suitable shape. As in this method it is necessary for the tube to be repeatedly strongly heated, much time is required and high costs are involved. For this reason it is sought to produce the. end thickening in one operation with the rolling of the tubes, whereby considerable economic advantages are obtained.

In the case of tubes which are finish-rolled by the pilgering method, it has been proposed, for instance for making an internal thickening of the wall at one end, to draw in the hollow body coming from the piercing rolls at one end by pressing or the like and to roll down this end over an offset mandrel. This method cannot, however, be employed in the case of tubes. made by rolling with skew rolls. In skew roll rolling mills with a mandrel stressed in compression, that is to say in rolling mills in which the tube is rolled on to the mandrel shaft, it has already beenproposed to pass the tube, after it has been rolled, without the mandrel through the rolls.

Skew roll rolling mills are also known, in which by reducing the diameter and the wall. thickness of the hollow body tubes which are ready for use are produced, in which however, in contradistinction to the usual rolling mills, the mandrel is so fixed on the mandrel bar that the latter is stressed in tension, so that the tube is rolled down off the mandrel bar.

In order to produce an end thickening in such skew roll rolling mills in a simple manner, according to the'invention the hollow piece coming from the piercing rolls is drawnin at its end in such a manner by upsetting it at the end or by forging it in two or more part dies or the like that, when introduced into the rolls", the constriction will bear against the forward end of the mandrel. The part of the hollow body projecting beyond the mandrel is then seized by the rolls, on the mandrel being forced between the latter and is reduced without mandrel pressure, that is to say, without reducing the wall thickness, to the external finished diameter of the tube. On the point of the mandrel engaging during the further forward motion of the mandrel, the wall of the hollow bloom commences to be rolled down in such a manner that according to the calibration of the mandrel a gradual compression of the thickened cylindrical part to the part of the tube having a wall of normal thickness is produced.

In the accompanying drawing Fig. 1 shows a skew roll rolling mill of the known kind, in longitudinal section, the figure representing the moment in which the blank which is drawn in at the end is just being introduced with the mandrel between the rolls.

Fig. 2 shows the same rolling mill, the tube being positioned between the rolls with the mandrel in the normal position, while the rolled down thickened end has left the rolls.

According to the invention the hollow bodies 3 coming from the piercing rolls pass, as they travel to the reducing skew rolls, a press or a hammer (not shown) ,where, by upsetting it at the end or forging it in a die, the constriction 4 (Fig. l) at one end is produced. As the hollow body leaves the piercing rolls at a sufliciently high temperature and the operation of drawing it in can be carried out in a few seconds, there is no serious loss of heat and the hollow body can be passed directly after being forged to the skew rolls.

In the ,rolls 5 the withdrawn mandrel 6 is pushed into the blank, until the mandrel head I bears against the constriction 4. On the mandrel 6 being pushed further forward the hollow body 4 is pushed between the rolls until the blank is seized by the rolls 8 (Fig. 1). The constriction 4 will then bear against the forward end I of the mandrel and is reduced by the rolls without the mandrel being forced forward to the external finished diameter of the tube, the thickening 9 Fig. 2) being thus produced. The mandrel then moves forward into the final rolling position (Fig. 2) the part I!) adjoining the thickening 9 gradually widening, corresponding to the-forward motion of the mandrel, to the internal diameter of the finished tube. It is possible to determine the quantity of material in the thickened end by the length and the shapeimparted to the constricted part of the hollow body and it is also possible to influence this quantity by the shape of the mandrel end.

What I claim is:

1. A method of producing a thickening of the wall at the end of tubular. bodies made by means of skew rolls coacting with a mandrel, consisting in piercing the end of the blank, constricting the said pierced endin such a manner that, on the blank being introduced between the rolls,.the constricted end will bear against the forward end of the mandrel and be reduced by the rolls without any forward pressure being exerted by the mandrel and thereupon finish-rolling the blank.

2. A method of producing a thickening at the end of tubular bodies, as claimed in claim 1, in which the quantity of material in the end thickening to be formed by rolling is determined by the shape given to the constricted end of the pierced. part of the blank and the shape of the 1-0 mandrel end.

3. A method of rolling out a tube with an internally thickened end from a tubular blank in a skew roll rolling mill, using a mandrel, consisting in drawing the tubular blank in at its end in such a manner that the drawn in part will bear against and project beyond the forward end I down the wall of the blank between the rolls and 10 the mandrel.

HEINRICH ESSER. 

